Re: [PATCH 2/2] arm: qcom: Add SMP support for Cortex-A7

[Stephan Gerhold <stephan@gerhold.net>]

Hi,

On Thu, May 13, 2021 at 05:34:42PM +0200, Bartosz Dudziak wrote:
> Implement support for Cortex-A7 CPU release sequence.
> 
> Signed-off-by: Bartosz Dudziak <bartosz.dudziak@snejp.pl>
> ---
>  arch/arm/mach-qcom/platsmp.c | 72 ++++++++++++++++++++++++++++++++++++
>  1 file changed, 72 insertions(+)
> 
> diff --git a/arch/arm/mach-qcom/platsmp.c b/arch/arm/mach-qcom/platsmp.c
> index 630a038f45..10780bf14a 100644
> --- a/arch/arm/mach-qcom/platsmp.c
> +++ b/arch/arm/mach-qcom/platsmp.c
> @@ -29,6 +29,7 @@
>  #define COREPOR_RST		BIT(5)
>  #define CORE_RST		BIT(4)
>  #define L2DT_SLP		BIT(3)
> +#define CORE_MEM_CLAMP		BIT(1)
>  #define CLAMP			BIT(0)
>  
>  #define APC_PWR_GATE_CTL	0x14
> @@ -75,6 +76,63 @@ static int scss_release_secondary(unsigned int cpu)
>  	return 0;
>  }
>  
> +static int cortex_a7_release_secondary(unsigned int cpu)
> +{
> +	int ret = 0;
> +	void __iomem *reg;
> +	struct device_node *cpu_node, *acc_node;
> +	u32 reg_val;
> +
> +	cpu_node = of_get_cpu_node(cpu, NULL);
> +	if (!cpu_node)
> +		return -ENODEV;
> +
> +	acc_node = of_parse_phandle(cpu_node, "qcom,acc", 0);
> +	if (!acc_node) {
> +		ret = -ENODEV;
> +		goto out_acc;
> +	}
> +
> +	reg = of_iomap(acc_node, 0);
> +	if (!reg) {
> +		ret = -ENOMEM;
> +		goto out_acc_map;
> +	}
> +
> +	/* Put the CPU into reset. */
> +	reg_val = CORE_RST | COREPOR_RST | CLAMP | CORE_MEM_CLAMP;
> +	writel(reg_val, reg + APCS_CPU_PWR_CTL);
> +
> +	/* Turn on the BHS, set the BHS_CNT to 16 XO clock cycles */
> +	writel(BHS_EN | (0x10 << BHS_CNT_SHIFT), reg + APC_PWR_GATE_CTL);
> +	/* Wait for the BHS to settle */
> +	udelay(2);
> +
> +	reg_val &= ~CORE_MEM_CLAMP;
> +	writel(reg_val, reg + APCS_CPU_PWR_CTL);
> +
> +	reg_val |= L2DT_SLP;
> +	writel(reg_val, reg + APCS_CPU_PWR_CTL);
> +	udelay(2);
> +
> +	reg_val = (reg_val | BIT(17)) & ~CLAMP;
> +	writel(reg_val, reg + APCS_CPU_PWR_CTL);
> +	udelay(2);
> +
> +	/* Release CPU out of reset and bring it to life. */
> +	reg_val &= ~(CORE_RST | COREPOR_RST);
> +	writel(reg_val, reg + APCS_CPU_PWR_CTL);
> +	reg_val |= CORE_PWRD_UP;
> +	writel(reg_val, reg + APCS_CPU_PWR_CTL);
> +

I think you forgot to add

	iounmap(reg);

here :)

> +out_acc_map:
> +	of_node_put(acc_node);
> +out_acc:
> +	of_node_put(cpu_node);
> +
> +	return ret;
> +}
> +
>  static int kpssv1_release_secondary(unsigned int cpu)
>  {
>  	int ret = 0;
> @@ -281,6 +339,11 @@ static int msm8660_boot_secondary(unsigned int cpu, struct task_struct *idle)
>  	return qcom_boot_secondary(cpu, scss_release_secondary);
>  }
>  
> +static int cortex_a7_boot_secondary(unsigned int cpu, struct task_struct *idle)
> +{
> +	return qcom_boot_secondary(cpu, cortex_a7_release_secondary);
> +}
> +
>  static int kpssv1_boot_secondary(unsigned int cpu, struct task_struct *idle)
>  {
>  	return qcom_boot_secondary(cpu, kpssv1_release_secondary);
> @@ -315,6 +378,15 @@ static const struct smp_operations smp_msm8660_ops __initconst = {
>  };
>  CPU_METHOD_OF_DECLARE(qcom_smp, "qcom,gcc-msm8660", &smp_msm8660_ops);
>  
> +static const struct smp_operations qcom_smp_cortex_a7_ops __initconst = {
> +	.smp_prepare_cpus	= qcom_smp_prepare_cpus,
> +	.smp_boot_secondary	= cortex_a7_boot_secondary,
> +#ifdef CONFIG_HOTPLUG_CPU
> +	.cpu_die		= qcom_cpu_die,
> +#endif
> +};
> +CPU_METHOD_OF_DECLARE(qcom_smp_cortex_a7, "qcom,cpss-acc", &qcom_smp_cortex_a7_ops);
> +

I'm a bit curious about the name "CPSS". Is that something you came up
with yourself similar to KPSS? There is a slight naming collision here
with the "Chip peripheral subsystem" (CPSS) on APQ8064E (Snapdragon 600),
see https://developer.qualcomm.com/download/sd600/snapdragon-600-device-spec.pdf

Thanks,
Stephan